B&Q is proposing to switch its horticultural operations from Coventry to Radlett in Hertfordshire, which could results in workers losing their jobs.
The move will take place in November and will affect 76 workers at national contractor Wincanton.
All affected Wincanton employees have been given the option to transfer with their current role to the new site, just inside the M25 motorway.
A Wincanton representative said: "Following a strategic review of its operations, we can confirm that B&Q has proposed to relocate its horticulture operation from Coventry to Radlett, effective November 2014.
"Should the proposal go ahead, all affected Wincanton employees will have the option to transfer with their current role to the new site.
"We are entering into immediate consultation with affected employees."